Flower Bucket Question

So I'm just about to start cutting to bottom out of said flower buckets to put into grow bags as I did last year. It seems a little silly filling flower buckets with compost and sitting the buckets in grow bags.
Now I know a lot of you lovely grapes just plant your tomatoes in your flower buckets so I'm kinda thinking of tryin' it this year. I'm just a little worried about watering.
My tomato greenhouse is on a lottie so I only water in there in mornings and evenings.
Will this be enough? I used the growbags last year as a reservoir to hold water to last them through the day.

I had 6 holes in the bottom, and when I emptied them out (watered morning and evening too..) the compost at the very bottom was very wet - obviously the holes were too small... so sort of same principle as Bren's I guess

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